ACTG 306 was designed to test the hypothesis that 3TC would be uniquely effective in combination with ZDV, and that the combination of ZDV/3TC would be superior to either ddl/3TC. It also tested the hypothesis that ddl/3TC and d4T/3TC regimens would suppress HIV-1 replication more effectively than ddl or d4T monotherapy. Results of the primary analysis at week 24 were reported in an Executive Summary dated August 4, 1997. The analysis found that the combination of d4T plus 3TC had significantly greater antiviral activity than d4T alone; there were no significant differences between the d4T/3TC and ADV/3TC arms. By contrast, the combination of ddl plus 3TC was not significantly more potent than ddl alone nor were there any significant differences between the two ddl/3TC and ZDV/3TC arms.